DIGITALE TELEFONIE MIT IN ZEITSCHLITZEN GESENDETEN KONTROLLNACHRICHTEN ZUR HF- FREQUENZZUTEILUNG

In a system in which control messages are transmitted in predetermined time slots within fixed length time frames from a first transmitting and receiving unit to a second transmitting and receiving unit, the second unit listens on a selected RF carrier frequency for an incoming message, the selected RF carrier frequency being selected from the class of RF frequencies available and preferred for use, the RF frequencies being classified dependent on whether communications on previously selected carrier frequencies have been successful.